This invention relates to casters and concerns in particular the braking device for casters for carts, wagons and the like used aboard passenger-carrying vehicles such as jet planes, railroad cars and ships.
A conventional caster consists of a rotary thrust bearing secured to the cart, a wheel for rolling on the floor, and a generally curved fork connected to the thrust bearing and holding the wheel axle by its bifurcated ends. The fork and wheel as one are capable of swiveling motion around the center of rotation of the thrust bearing. Means are also provided for braking the wheel. The fork is so curved that the wheel axis is not directly under the center of the bearing but is offset therefrom. Due to this offset relationship, movement of the cart causes the fork to swivel to turn and bring the wheel to the trailing side of the cart. There is, however, no means of braking this swiveling motion.
When a cart equipped with conventional casters is in service aboard an airliner, and is at standstill in braked condition, its casters are all oriented in a direction on the trailing side of the previous direction of cart movement. When the plane banks, the cart experiences a push exerted by by the floor and, depending on the direction of this push relative to the orientation of the casters, the casters may swivel to reorient themselves, causing the cart to jog or jolt. When the plane rocks or pitches, the cart may shake or sway to and fro, forcing the articles on it to rattle or even spill liquid contents. The present invention purports to prevent such jogging, jolting and shaking motions of the cart by providing a novel means by which a braking force can be simultaneously applied to the wheel and to the thrust bearing.
According to the present invention, a caster is provided with a brake member which extends between the forked legs of the caster and serves simultaneously to brake the caster wheel and oppose the swiveling tendency of the caster fork. The brake member has one end for frictionally engaging the caster wheel to prevent rolling movement and another end for frictionally engaging an annular surface attached to the caster base to prevent swiveling movement. An actuator is provided for moving the brake member to and from its braking position.
The details of the braking device according to my invention will be made clear from the preferred embodiment thereof described below and illustrated in the attached drawings.